The present invention relates to a method of manufacturing an article, particularly to a method of manufacturing an article from sheet metal workpieces and more particularly to a method of manufacturing an article from sheet metal workpieces by diffusion bonding and hot forming.
It is known to manufacture an article from sheet metal workpieces by diffusion bonding and hot forming. In particular it is known to manufacture fan blades and fan outlet guide vanes for gas turbine engines by diffusion bonding a plurality of titanium sheet metal workpieces and then hot forming or superplastically inflating the diffusion bonded titanium sheet metal workpieces. These manufacturing process are described in our European patent EP0568201B1, European patent application EP1092485A1 and UK patent GB2306353B.
A problem with the manufacture of a fan outlet guide vane is that attachment features are required on the radially inner and outer ends of the fan outlet guide vane to enable the fan outlet guide vane to be attached at the radially inner end to a core engine casing and to be attached at the radially outer end to a fan casing.
Currently titanium pieces are forged to produce locally thickened end portions suitable for a fastener, a bolt, to pass through to retain the fan outlet guide vane on the core engine casing or fan casing. The titanium piece is machined to size and is welded to the radially inner end or radially outer end of the fan outlet guide vane.
This process is costly and the fan outlet guide vanes are relatively heavy due to the solid radially inner end portion and radially outer end portion of the fan outlet guide required to attach the fan outlet guide vane to the core engine casing and the fan casing.
A problem with the manufacture of a fan blade is that attachment features are required on the radially inner end of the fan blade to enable the fan blade to be attached at the radially inner end to a fan rotor.
Currently blocks of titanium are diffusion bonded to the surfaces of the titanium workpieces at the radially inner end of the fan blade to locally thicken the fan blade so that a dovetail root or firtree root may be formed as described in GB2306353B.
Accordingly the present invention seeks to provide a novel method of manufacturing an article from sheet metal workpieces which reduces, preferably overcomes, the above mentioned problems.
Accordingly the present invention provides a method of manufacturing a sheet metal article comprising forming a sheet metal article from at least one sheet metal workpiece, weld-depositing metal at at least one predetermined position and in a predetermined shape to build up a feature to net shape at the at least one predetermined position on the sheet metal article.
Preferably the method comprises selecting at least two sheet metal workpieces, assembling the at least two sheet metal workpieces in a stack of sheet metal workpieces, sealing the edges of the stack of sheet metal workpieces, diffusing bonding the stack of sheet metal workpieces in areas other than a predetermined pattern to form an integral structure, weld-depositing metal at at least one predetermined position and in a predetermined shape to build up a feature to net shape at the at least one predetermined position on the integral structure, and heating the integral structure and internally pressurising the interior of the integral structure to hot form at least one of the at least two metal workpieces to form a hollow integral structure of predetermined shape.
Preferably the method comprises weld-depositing metal at at least one predetermined position at one end of the hollow integral structure.
Preferably the method comprises weld-depositing metal at two predetermined positions.
The method may comprise weld-depositing metal at both ends of the hollow integral structure, weld-depositing the metal in a predetermined position and in a predetermined shape to build up features to net shape at both ends of the hollow integral structure.
The method may comprise weld-depositing metal at both sides at one end of the hollow integral structure, depositing the metal in a predetermined position and in a predetermined shape to build up a feature to net shape at both sides of the hollow integral structure.
The method may comprise weld-depositing metal at both sides at both ends of the hollow integral structure, depositing the metal in a predetermined position and in a predetermined shape to build up a feature to net shape at both sides at both ends of the hollow integral structure.
The method may comprise weld-depositing metal at one end and at one side of the hollow integral structure, depositing the metal in a predetermined position and in a predetermined shape to build up a feature to net shape at one end and on one side of the hollow integral structure.
Preferably the article is a fan outlet guide vane or a compressor vane.
Preferably the method comprises weld-depositing the metal to build up a boss at at least one end of the article.
Preferably the method comprises drilling an aperture through the boss.
Alternatively the article is a fan blade or compressor blade.
The method may comprise weld-depositing the metal to build up a dovetail root or a firtree root at one end of the article.
Preferably the sheet metal article comprises titanium or a titanium alloy.
Preferably the method comprises weld-depositing titanium or a titanium alloy.
Preferably the titanium alloy comprises 6 wt % Al, 4 wt % vanadium and the balance is titanium plus incidental impurities.
Alternatively the sheet metal article comprises a nickel alloy. Alternatively the method comprises weld-depositing a nickel alloy. Preferably the nickel alloy comprises 19 wt % Cr, 18 wt % Fe, 5 wt % Nb, 3 wt % Mo, 0.9 wt % Ti, 0.5 wt % Al and the balance Ni plus incidental impurities.
Preferably a stop off material is applied in a predetermined pattern to at least one surface of at least one of the at least two sheet metal workpieces before assembling the at least two sheet metal workpieces in a stack of sheet metal workpieces.